Yeah, I'll double check the connections. But I'd really like to find the fuse. I suppose 15 amps would be too small. I do have a solar panel. It's never worked as far as I can tell so this fuse would make sense.

As far as following the cable from the inverter to the batteries... easier said than done. There's a whole compartment between them that doesn't look very accessible.

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Great re the multimeter. First check the voltage right on the battery terminal with no load and without AC supplied to the coach, check the voltage to the DC output connection of the charger. If you have the same voltage there as at the battery, you have connectivity, but does not necessarily mean all connections are good, because there should be a no or at least a low load. So making certain connections are good from the getgo is a good idea. This test is another way of checking continuity across any fuse and associated circuitry. No need to find the fuse if you have the same voltage at both ends of the circuit.

You must have sufficient DC voltage to activate the safety relay in the charger, (not certain what that requirement is for your unit) but the charger output will be shut down if the voltage on the battery is too low.

Then put external AC on (shore or gen power) and measure the battery voltage again and make certain the charger has AC voltage, it is turned on and all breakers are good. Measure the battery voltage again - it should be higher if the charger is working.

Good luck, your mulitmeter is you best friend to help diagnose electrical problems.

I presume you have discovered there was no change in voltage level at the batteries when you applied AC voltage to the coach. What was that voltage on the batteries and at the DC output wires of the charger?

Is the inverter producing AC voltage on its output given there are new batteries installed!

Did you determine if AC voltage was being provided to the charger input circuitry?

Just thinking of other options now such as: Do you have DC voltage inside the coach with the new batteries installed?

Sometimes the charger will not work when that switch is off or the relay it controls is open. Don't know if your coach is wired that way or not but it is worth a shot to look at it and likewise there would not be any AC voltage output from the inverter with that switch/relay off.

Good luck - keep looking and measuring voltages at various locations until you have found the absolute cause of the problem. It becomes a matter of elimination.

You have indeed determined the battery is not being charged by the converter, however you have yet to determine if the converter is faulty or some other factor is in play, Please see my previous post re other tests you might do to isolate this further.

And... the new batteries power the coach very well. At first the batteries showed a full charge. They powered the lights and I made a pot of coffee no problem. Now after a day or so the panel is showing low battery even though the charger has been running from shore power all night.

The only time the house batteries charge is when the engine is running. This hasn't been an issue in the past because we were driving 4 to 8 hours per day. Now that were just sitting the charging issue is a problem.

I'm not sure how to test if AC is getting to the charger circuit. I have it open and the big DC points are obvious but it's not obvious where to check the AC input. There are big white cables going in at the bottom but they're covered in plastic.

I would definitely rather repair this unit than pay $1000 for a new one. Plus it may need a new remote, cables, installation etc since this unit is no longer made.

I wonder if the Xantrex unit that looks exactly the same can be switched out for this one.

The white wires will be 120Vac. With the cover off, can you see the back side of any AC circuit breakers? If yes, you could measure the AC at those breakers, however I suggest if you are not familiar with working on live AC circuits, it is time to bring in someone who has the savvy to do it,

Without having a 3 stage charger, you will end up ruining your new batteries, but as an interim fix, you might want to get a cheaper charger until you fix or replace it with a 3 stage unit. If you buy a decent 3 stage charger now you will have a backup if you do get the current unit working,

A good 3 stage 50A charger would be less than $400. Suggest you Google options available, but connecting and storage should be factored in.